- Group 1 (high risk): Patients receive one course of regimen A comprising CTX IV over 15 minutes on days 1-4; VCR IV on days 1, 8, and 15; doxorubicin (DOX) IV on days 1 and 2; ARA-C IV over 3 hours every 12 hours on day 1; ARA-C IT on day 4; and MTX IT on days 8 and 12. Patients then receive one course of regimen B comprising ifosfamide IV over 30 minutes on days 1-5, etoposide IV over 1 hour and MTX IV on days 1-3, VCR IV on day 8, ARA-C IT on days 1 and 4, and MTX IT as in regimen A. Patients then receive a second course of regimen A, followed by a second course of regimen B.